This present invention generally relates to plant cutting appliances, in particular brush cutters.
For several years, there have been developed different forms of cutting strings or filaments which are designed to be mounted on a cutting head, driven by an electric or thermal engine, so that the rapid rotation of the head drives the string or strings so that they tend to adopt a rectilinear extension under the effect of the centrifugal force. These strings are typically formed of a polyamide extrusion.
The oldest of these strings have a circular section and are smooth along their entire length, and recently developed strings have various sections, designed to improve the cutting quality (presence of edges, etc.) and/or the longevity of the string, and/or to reduce the noise of the appliance in operation by acting on the turbulences.
Thus the prior strings may include edges, grooves, furrows, or local deformations, along their entire length.
Furthermore, there are strings called aerodynamic strings, for example in the form of an airplane wing profile, water drop, or ellipse (see for example, U.S. Pat. No. 5,761,816).
Such strings have certain advantages linked to their improved penetration in the air. For example, less power is required for the engine, and they may also provide less operating noise, and overall a better cutting efficiency.
Such strings, which present a limited height, nevertheless present the inconvenience of being fragile. In particular, the accumulated rotation speed of these profiled strings allows increasing the intensity of shocks against the plants, and the small height of the string significantly increases its risk of breaking. The use of such strings for large jobs is therefore limited.
It is an object of this invention to provide new cutting strings that present advantages that are similar to those offered by existing profiled strings in terms of air penetration, but that are more robust and better adapted for large jobs.